High voltage acceleration tube structure



Nov. 11, 1 969 E. E. BLIAMPTI S L 3,478,

HIGH VOLTAGE ACCELERATION TUBE STRUCTURE Filed April 13, 1967 INVENTOR EMMANUEL E. BLIAMPTIS HUBERT R.Q N

f ATTORNEY United States Patent 3,478,241 IIIGH VOLTAGE ACCELERATION TUBE STRUCTURE Emmanuel E. Bliamptis, Lexington, and Hubert R. Quinn,

Peabody, Mass., assignors to High Voltage Engineering Corporation, Burlington, Mass., a corporation of Massachusetts Filed Apr. 13, 1967, Ser. No. 630,564 Int. Cl. Hh 5/02; H01j 1/52, 19740 US. Cl. 313-63 4 Claims ABSTRACT OF THE DISCLOSURE A novel acceleration tube structure composed of alternating insulating rings and conductive electrodes for use in high voltage accelerators which can be mechanically held in compression without the use of adhesives by a surrounding insulating shell such that it can be more easily and cheaply assembled and can be readily disas sembled for cleaning, inspection or repair.

BACKGROUND OF THE INVENTION This invention relates generally to sealed off high voltage acceleration tubes. In particular it relates to those acceleration tubes made up of laminated glass rings alternated with metallic electrodes. Such tubes were first produced by making the metal electrodes of a material of approximately the same coelficient of expansion as the glass sections because heating of'the glass sections to the softening point of the glass was required to effect a seal between the glass rings and the metal planes. An improvement of this technique was described in the US. Patent to Trump and Cloud, No. 2,460,201 dated Jan. 25, 1949. In this patent there was described a method of laminating such tubes without softening the glass by using a plastic bonding material between the glass sections and the metal electrodes.

This latter method is still widely used today, however, both methods produce tubes which are difficult to rework and disassemble for cleaning, repair, study, or the like.

SUMMARY OF THE INVENTION The present invention sets forth a novel acceleration tube which is mechanically held in compression. The acceleration tube produced by following the teachings of the present invention retains all the advantages of the prior art as regards electrical properties and yet has the additional advantage of being readily non-destructively demountable and repairable.

Broadly speaking the advantages of the present invention are realized in an acceleration tube comprising a series of glass rings interposed with metallic electrodes all surrounded by a bisected dielectric shell which supports compression plates at either end thereof.

BRIEF DESCRIPTION OF THE DRAWING The single figure is an exploded partially broken away view of an acceleration tube built in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the single figure there is illustrated an acceleration tube useful in high voltage acceleration apparatus such as are sold by High Voltage Enginering Corporation under the trade name Van de Graalf. Basically the acceleration tube consists of a column composed of a number of alternating glass or other insulating rings and metal electrode rings or ring like diaphragms or disks 12 alternately spaced and maintained together in compression.

3,478,241 Patented Nov. 11, 1969 ice Generally the metal electrodes lie on planes perpendicular to or at appropriate small inclinations to the axis of the would be approximately 2 feet. Larger sections up to 8,

feet are common. The diameter tube will vary with the voltage and for the 2,000,000 volt 2 foot length described above the external diameter of the tube would be about 3 inches and the diameter of the aperture 14 in each electrode would be about 1 inch. Of course for larger tubes these diameters will also be larger. For example, the longest tubes have external diameters of 8 inches or more.

Inasmuch as the invention is concerned with the holding together of the alternated glass rings and metal electrodes it is unnecessary to disclose in detail or to describe those auxiliary items such as cathodes and anodes which would be located on either end of such tubes. Moreover, since such acceleration tubes are well known and familiar to those skilled in particle accelerators and since description of their uses may be found in the US. Patent to R. J. Van de Graatf, No. 1,991,236 dated Feb. 12, 1935 and 2,230,473 dated Feb. 4, 1941 the inclusion of a description of their uSe herein is believed unnecessary.

In the present invention the metal electrode thickness and the glass ring thickness can be of any desired value but must be sufficient to resist puncture by the accelerated beam. Any other dielectric material such as plastic or the like may be used to replace the glass ring provided it has an insulating capability suitable to the applied voltage in a vacuum. The herein described accelerator tube can also be designed with the inside wall of the insulating rings contoured, corrugated or angled as desired to increase their voltage holdoif capabilities i.e. their flash-over strength in vacuum.

The insulating rings 10 and the electrodes 12 are placed serially in the lower frame 16 and the upper frame 18 of the shell mated thereon. For assurance that the glass and electrodes 12 tightly mate so as to accommodate a vacuum within the accelerator tube it is necessary that the surfaces of the glass rings be ground optically flat and the surfaces of the metal electrodes provided with a soft material which will crush and form itself in accordance with the contours of the glass surface. For best results are noted above the surfaces of the glass rings are ground optically flat and the metal electrodes coated or plated with a soft material such as indium or gold. Both frame halves 16 and 18 are identical and formed of glass or other suitable dielectric insulating material. Each frame is provided with a large longitudinal groove 20 whose radius is the same as the external radius of rings 10 or electrodes 12 such that when the frames 16 and 18 are mated there is provided a central opening which extends the length of the frame whose diameter will accept the rings 10 and the electrodes 12. Preferably the grooves should be so mated that the rings and planes are properly aligned in each shell half. Because it is desirable to bridge each insulating ring 10 with external resistors 22 which extend between the stacked electrodes provisions for electrical contact must be made. This is accomplished by providing along or near the mating faces of the frames a plurality of radial grooves 24 which can accommodate conductive leads. These grooves 24 are produced in the frames in line with the place of final positioning of the electrodes.

Alignment of the electrodes 12 in the frame is accomplished by providing each electrode with a pair of diametrically opposed alignment keys 26 which fit into side grooves 28 and 30 provided on either side of groove 20 in each frame half. Following arrangement of the electrodes and rings in the lower frame half and electrically connecting each electrode to the appropriate external resistive connection the top frame half 18 is set over the lower half and end plates 32 secured to each end of the frames by a plurality of bolts 34, which pass through holes 36 provided in plates 32 into longitudinally tapped holes 38, which are provided in the ends of each frame half. For better electrical potential distribution metallic paths 40 are deposited or otherwise laid down on the outside surface of the frame halves. These conductive strips are connected to the resistive network extending between electrodes. If desired the radial grooves 24 may also be plated or otherwise coated with conductive material to assure that the parts 40 are in contact with its respective electrode.

It is of course understood that the stacked plurality of electrodes and insulating glass rings should be of a dimension such that they are slightly longer than each of the respective frame halves so that when the end plates 32 are bolted onto the ends of the frame halves a suitable compressive force can be applied to the stacked arrangement of electrodes and insulating rings.

Instead of plated paths on the surface metal straps may be advantageously used. Such straps will serve in a dual capacity in that they not only act as potential distribution elements but also can be used to keep the halves together. The use of such straps can thus lead to the elimination of transverse bolting if mating surfaces 86 and 87 are made to hold a vacuum.

The described construction results in an acceleration tube in which the equipotential planes and glass insulators are inserted into the column without adhesive or glass to metal bonding such that its assembly is simpler and less expensive and its disassembly non-destructive.

Having now described an acceleration tube and the method of making it it is to be understood that although specific terms are employed they are not for purposes of limitation and the scope of the invention is limited only by the appended claims.

We claim:

1. A self supporting, high voltage, high vacuum acceleration tube for charged particle accelerators comprising a plurality of apertured planar disk metallic elec trodes alternated with insulating rings maintained in compression in a bisectible separable dielectric shell by end plates, said frame shell having electrical potential distribution paths laid on the exterior surface thereof at predetermined intervals and in the plane of the electrodes and means for maintaining a compressive force on said electrodes and said rings, each of said electrodes comprising a disk having a pair of shaped alignment keys thereon said keys being located on a diameter of said disk and said shell comprising two main halves each half having a central longitudinal groove therein whose shape conforms to the shape of said rings and said electrodes and having a pair of longitudinal side grooves, each of said side grooves matching the shape of said keys, each of said shellhalves being provided with means for coupling said end plates thereto.

2. The tube of claim 1 wherein said paths are metallic deposits on said shell halves.

3. The tube of claim 1 wherein said paths comprise metallic straps holding said halves in compression.

4. The tube of claim wherein said electrodes are coated with soft metallic metals and said rings have optically flat surfaces adapted to mate with said electrodes.

References Cited UNITED STATES PATENTS 2,429,824 10/1947 Koch et al. 31362 2,460,201 1/1949 Trump et al 313313 2,519,007 8/ 1950 Wilson 313-61 2,950,412 8/1960 Albert 313250 3,329,848 7/1967 Adachi et a1 '31363 JAMES W. LAWRENCE, Primary Examiner D. OREILLY, Assistant Examiner US. Cl. X.R. 

